Gegendrehung Und Winkelsinn in Der Orientierung Von Lithobius Forficatus L. Teil Iii: Ergänzende Untersuchungen Zur Verrechnung Von Winkelfolgen

The centipede Litkobius forficatus L. (Myriapoda) when forced to deviate from its initial course by passing through corridors containing sharp bends performs opposing (reverse) turns at the corridor's exits. The magnitudes of opposite turning responses appears to be a function of the size of the induced turns ("angle sense"). If corridors are used containing distances of 4 cm, entrance to turn and turn to exit, a relation of 1:0.7 between stimulus and response (induced turn : opposing turn) is measured for induced turn-angles up to about 120°; greater angles lead to a relative decrease in response up to a limit of 270° (Fig. 12). Increasing the distances from induced turn to choice point (corridor-exit) by an additional 4 cm (4:8 cm corridors) decreased opposite turning, resulting in the relation 1:0.49 between stimulus and response. Using corridors with two sequential turns and proportions of 4:4:4 cm demonstrates adding or subtracting mechanisms of stimulus sequences. However, due to the decreasing influence of increasing distances after an induced turn, passing through the second turn of the angle sequence can be seen as an increase of distance after the first angle, and therefore a decreasing response which must be added to the second turn (Fig. 1). An alternative addingmechanism could be a linear addition without the decreasing ("unloading") effect of distance referred to above. Sequences with left-right or right-left turns cannot be used to decide between the two possible mechanisms because both lead to identical degrees of response (Fig. 2). Experiments were performed using sequences of the same or opposed induced turns with various corridor distances. It could be demonstrated that, although decreasing effects of straight distances after turns were acting, linear additions of induced turn sequences were possible without the influence of unloading, but limited by the capacity of the neural store (Fig. 13).